Embodiments of the invention relate generally to integrated circuits and, more particularly, to the structure of an electrically programmable fuse (e-fuse) and methods of fusing an e-fuse and/or monitoring leakage in a semiconductor structure.
Many integrated circuits are made up of millions of interconnected devices, such as transistors, resistors, capacitors, and diodes, on a single chip of a semiconductor substrate. Semiconductor integrated circuits (“semiconductors”) can also include one or more types of memory, such as CMOS memory, antifuse memory, and e-fuse memory.
E-fuses are usually integrated into semiconductors by using a narrow strip of conducting material (metal, poly-silicon, etc.) between wiring or electrical contacts. This narrow strip of conducting material is sometimes called a “fuse link.” The contacts or wiring can be in the form of two pads, sometimes referred to as “vias” or an anode/cathode pair. “Vias” can connect one layer of a semiconductor to another. Applying a programming current (Iprog) to the e-fuse destroys a portion of the link, and causes resistance of the e-fuse to greatly increase. This process can be known as “fusing” or “programming” the e-fuse. The fuse state (i.e., whether a portion of the fuse is destroyed) can be read using a sense circuit. An e-fuse can be fused by causing electromigration to occur within the fuse link, creating a “void” in all or part of the fuse link section.
Fusing an e-fuse via electromigration can offer a controlled, reliable method for fusing an e-fuse. Controlling the appearance of voids in back end of line (BEOL) fuses, however, can be difficult to achieve because of process changes during the development cycle. Specifically, improvements to back end of line manufacture and design (e.g., smaller scale devices) have caused the appearance and location of voids during fusing to become unpredictable.